I read in sci.electronics.design that Ian White, G3SEK
wrote (in ) about
'Measuring radiation resistance', on Mon, 8 Dec 2003:
I'm looking forward
to making some outdoor antenna measurements using the new N2PK vector
network analyser

Is N2PK a call-sign? Are there any details of this analyser on the
Internet?
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

John Woodgate wrote:
I read in sci.electronics.design that Ian White, G3SEK
wrote (in ) about
'Measuring radiation resistance', on Mon, 8 Dec 2003:
I'm looking forward
to making some outdoor antenna measurements using the new N2PK vector
network analyser

Is N2PK a call-sign? Are there any details of this analyser on the
Internet?

Yes; it belongs to Paul Kiciak.

And yes -

The original website URL is:

Â*Â* http://users.adelphia.net/~n2pk/

Â*Â* There is also a mirrored website at:

Â*Â* http://www.qsl.net/n2pk/



Very briefly, it's a 0.05-60MHz VNA based on a DDS signal source feeding
the Device Under Test. Output from the DUT goes to a 'zero IF' detector
(multiplicative mixer) that converts to a DC signal level, which in turn
goes to an ADC.

The local oscillator for the detector is a second identical DDS,
programmed to the same frequency. Phase information is obtained by
making two sequential measurements, one with the LO at the same phase as
the signal source, and the second with the LO switched to 90deg.

Control is via the PC parallel port, which also accepts the signal level
data from the ADC. The support software includes full calibration
facilities (open/through for transmission measurements, and
open/short/load for reflection measurements with a bridge attachment).

For such a simple concept, the accuracy is astonishingly high,
approaching that of a commercial VNA. Paul Kiciak has investigated these
issues very thoroughly indeed, and the results are fully documented.

Everything is on the website, including full constructional information,
board layouts, software and extremely detailed documentation.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

John Woodgate wrote:
I read in sci.electronics.design that Ian White, G3SEK
wrote (in ) about
'Measuring radiation resistance', on Mon, 8 Dec 2003:
I'm looking forward
to making some outdoor antenna measurements using the new N2PK vector
network analyser

Is N2PK a call-sign? Are there any details of this analyser on the
Internet?

Yes; it belongs to Paul Kiciak.

And yes -

The original website URL is:

Â*Â* http://users.adelphia.net/~n2pk/

Â*Â* There is also a mirrored website at:

Â*Â* http://www.qsl.net/n2pk/



Very briefly, it's a 0.05-60MHz VNA based on a DDS signal source feeding
the Device Under Test. Output from the DUT goes to a 'zero IF' detector
(multiplicative mixer) that converts to a DC signal level, which in turn
goes to an ADC.

The local oscillator for the detector is a second identical DDS,
programmed to the same frequency. Phase information is obtained by
making two sequential measurements, one with the LO at the same phase as
the signal source, and the second with the LO switched to 90deg.

Control is via the PC parallel port, which also accepts the signal level
data from the ADC. The support software includes full calibration
facilities (open/through for transmission measurements, and
open/short/load for reflection measurements with a bridge attachment).

For such a simple concept, the accuracy is astonishingly high,
approaching that of a commercial VNA. Paul Kiciak has investigated these
issues very thoroughly indeed, and the results are fully documented.

Everything is on the website, including full constructional information,
board layouts, software and extremely detailed documentation.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

I read in sci.electronics.design that Ian White, G3SEK
wrote (in ) about
'Measuring radiation resistance', on Sat, 13 Dec 2003:
Yes; it belongs to Paul Kiciak.

And yes -

The original website URL is:

Â*Â* http://users.adelphia.net/~n2pk/

Â*Â* There is also a mirrored website at:

Â*Â* http://www.qsl.net/n2pk/



Very briefly, it's a 0.05-60MHz VNA based on a DDS signal source feeding
the Device Under Test. Output from the DUT goes to a 'zero IF' detector
(multiplicative mixer) that converts to a DC signal level, which in turn
goes to an ADC.

Thank you very much.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

I read in sci.electronics.design that Ian White, G3SEK
wrote (in ) about
'Measuring radiation resistance', on Sat, 13 Dec 2003:
Yes; it belongs to Paul Kiciak.

And yes -

The original website URL is:

Â*Â* http://users.adelphia.net/~n2pk/

Â*Â* There is also a mirrored website at:

Â*Â* http://www.qsl.net/n2pk/



Very briefly, it's a 0.05-60MHz VNA based on a DDS signal source feeding
the Device Under Test. Output from the DUT goes to a 'zero IF' detector
(multiplicative mixer) that converts to a DC signal level, which in turn
goes to an ADC.

Thank you very much.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

Perhaps you didn't see the earlier posts on the subject. The frequency
is 40Mhz (radio control band) and the tx output stage as it stands
puts out maximum power of 475mW with a 140 ohm resistor as load. I
only *need* 50mW ERP., however, so can stand to see quite a bit of
loss from an inefficient antenna. The antenna I will be using is a
telescopic whip - exactly the same set-up as you see with model
vehicle radio control transmitters- which is what it is, in fact.
It ain't rocket science.
Someone out there must know the radiation resistance of such a
telescopic whip (which has a ground plane of just around 16 square
inches contained within the remote control handset) and the best way
to couple it to a PA with a 140 ohm output impedance?

Google "electrically short"

Perhaps you didn't see the earlier posts on the subject. The frequency
is 40Mhz (radio control band) and the tx output stage as it stands
puts out maximum power of 475mW with a 140 ohm resistor as load. I
only *need* 50mW ERP., however, so can stand to see quite a bit of
loss from an inefficient antenna. The antenna I will be using is a
telescopic whip - exactly the same set-up as you see with model
vehicle radio control transmitters- which is what it is, in fact.
It ain't rocket science.
Someone out there must know the radiation resistance of such a
telescopic whip (which has a ground plane of just around 16 square
inches contained within the remote control handset) and the best way
to couple it to a PA with a 140 ohm output impedance?

Google "electrically short"

On Mon, 8 Dec 2003 07:58:57 +0000, "Ian White, G3SEK"
wrote:


You can't directly measure radiation resistance, because it's embedded
in loss resistances and usually reactance too. Also there's more than
one definition of radiation resistance: some would say that the
radiation resistance of a half-wave dipole depends on where and how it
is fed (centre, end, off-centre); while others would say that the
radiation resistance stays the same, and it's only the feedpoint
impedance that depends on the method of feed.

Since you can't measure it and there isn't even a universally agreed
definition, it's best to tiptoe quietly away from "radiation resistance"
before the Holy Wars begin...


I don't wish to participate in this real discussion since I have only
a vague memory of what we had at school over 30 years ago, and math -
and in particular integration - is not my strong side.
Could you suggest any values of what one could expect to find for
radiiation resistance for some variations of half wave dipoles,
dependent on wire size, height and other?

73
Jan-Martin, LA8AK
http://home.online.no/~la8ak/a.htm
--
remove ,xnd to reply (Spam precaution!)

On Mon, 8 Dec 2003 07:58:57 +0000, "Ian White, G3SEK"
wrote:


You can't directly measure radiation resistance, because it's embedded
in loss resistances and usually reactance too. Also there's more than
one definition of radiation resistance: some would say that the
radiation resistance of a half-wave dipole depends on where and how it
is fed (centre, end, off-centre); while others would say that the
radiation resistance stays the same, and it's only the feedpoint
impedance that depends on the method of feed.

Since you can't measure it and there isn't even a universally agreed
definition, it's best to tiptoe quietly away from "radiation resistance"
before the Holy Wars begin...


I don't wish to participate in this real discussion since I have only
a vague memory of what we had at school over 30 years ago, and math -
and in particular integration - is not my strong side.
Could you suggest any values of what one could expect to find for
radiiation resistance for some variations of half wave dipoles,
dependent on wire size, height and other?

73
Jan-Martin, LA8AK
http://home.online.no/~la8ak/a.htm
--
remove ,xnd to reply (Spam precaution!)

Download program DIPCAGE2 from website below.
---
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........


Could you suggest any values of what one could expect to find for
radiiation resistance for some variations of half wave dipoles,
dependent on wire size, height and other?